Bonding member and electrostatic chuck

ABSTRACT

A bonding member includes, a ceramics member having a concave portion, a metal member which has a convex portion fitted to the concave portion, a first bonding material which joins a bottom portion of the concave portion of the ceramics member and a tip portion of the convex portion of the metal member and has a porous structure including particles and brazing filler metal that covers a corner between tip and side portions of the metal member, and a second bonding material which includes brazing filler metal that joins a side portion of the concave portion of the ceramics member and a side portion of the convex portion of the metal member.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom prior Japanese Patent Application P2003-062040 filed on Mar. 7,2003; the entire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a bonding member including twoor more of different kinds of members by joining the different kinds ofmembers together. More particularly, the present invention relates to anelectrostatic chuck which can be suitably used in a semiconductormanufacturing device.

[0004] 2. Description of the Related Art

[0005] Conventionally, for bonding of a ceramics member and a metalmember, there is a method using a brazing material. However, in acooling operation after the bonding performed at high temperature, thereoccurs thermal stress caused by a difference in a coefficient of thermalexpansion between different kinds of members or between the members anda brazing material used for joining these different kinds of members.Accordingly, a bonding interface is peeled off or cracks occur in thevicinity of the bonding interface when one of the members is fragile.Thus, desired bonding strength and airtightness may not be obtained.Products, in which such problems as described above arise in amanufacturing process thereof, have to be disposed of as defectiveproducts. Thus, the problems described above contribute to increasingproduct costs of these bonding members. Moreover, if there is a heatcycle when the members are used, the problems described above ariseafter the members are used for a fixed period of time. Accordingly, theproblems also contribute to lowering reliability of the product.

[0006] In consideration of the present situation described above, therehas been studied a bonding method which maintains moderate bondingstrength between different kinds of members, without causing aphenomenon of lowering bonding strength due to thermal stress in thevicinity of a bonding interface during a cooling operation after bondingperformed at high temperature and without generating cracks in a coolingoperation for a member vulnerable to the thermal stress. For example,there is disclosed a method for obtaining a bonding layer by usingbrazing filler metal as a base and adding particles which lower thermalstress to the brazing filler metal (for example, see Japanese Patent No.3315919). Moreover, there is also disclosed a method for joiningdifferent kinds of members together when a width of a gap existingbetween wall surfaces of the different kinds of members in a fittingstructure portion is narrow (for example, see Japanese Patent Laid-OpenNo. 2001-10873). Furthermore, there is also disclosed a bonding adhesivecomposition which includes brazing filler metal and a mixture of atleast two kinds of particles different from the brazing filler metal inwettability (for example, see Japanese Patent Laid-Open No.2001-122673).

[0007] Moreover, as a product which requires bonding of a ceramicsmember and a metal member, for example, an electrostatic chuck used in asemiconductor process or the like is enumerated. In this electrostaticchuck, the ceramics member and the metal member are joined together in aportion of a substrate, which has built-in electrodes and is made ofceramics or the like, and a terminal, which supplies power to thebuilt-in electrodes and is made of gold-plated molybdenum or the like.

[0008] As described above, there have been known various methods forjoining a ceramics member and a metal member, which never cause aphenomenon of lowering bonding strength nor generate cracks in a coolingoperation for a member vulnerable to thermal stress. However, even byusing the methods described above, residual stress is likely to beconcentrated in a corner portion when different kinds of members arejoined by adopting a structure in which a concave portion is fitted to aconvex portion. Therefore, cracks sometimes occurred.

SUMMARY OF THE INVENTION

[0009] A first aspect of the present invention is to provide a bondingmember, including, a) a ceramics member having a concave portion, b) ametal member which has a convex portion fitted to the concave portion,c) a first bonding material which joins a bottom portion of the concaveportion of the ceramics member and a tip portion of the convex portionof the metal member and has a porous structure including particles andbrazing filler metal that covers a corner between tip and side portionsof the metal member, and d) a second bonding material which includesbrazing filler metal that joins a side portion of the concave portion ofthe ceramics member and a side portion of the convex portion of themetal member.

[0010] A second aspect of the present invention is to provide anelectrostatic chuck for absorbing an object to be processed, theelectrostatic chuck, comprising, a) a substrate which includes anelectrode therein and has a concave terminal bonding hole, b) a terminalwhich is a member made of a different material from that of thesubstrate and supplies power to the electrode, c) a bottom portionbonding material which joins a bottom portion of the terminal bondinghole and a tip portion of the terminal and has a porous structureincluding particles and brazing filler metal that covers a cornerbetween tip and side portions of the terminal, and d) a side portionbonding material which includes brazing filler metal that joins a sideportion of the terminal bonding hole and the side portion of theterminal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1A is a cross-sectional view of an electrostatic chuckaccording to an embodiment of the present invention.

[0012]FIG. 1B is an enlarged view of a bonding portion between aterminal and an electrode, which is shown in FIG. 1A.

[0013]FIG. 1C is an enlarged view of a corner portion of the terminaland a terminal bonding hole, which is shown in FIG. 1B.

[0014]FIG. 2 is a flowchart showing a method for manufacturing theelectrostatic chuck according to the embodiment of the presentinvention.

[0015]FIG. 3 is a flowchart showing a method for joining the terminal ofthe electrostatic chuck according to the embodiment of the presentinvention.

[0016]FIG. 4A is a cross-sectional SEM photograph of a terminal bondingportion of an electrostatic chuck in example 1.

[0017]FIG. 4B is an enlarged view of section A in FIG. 4A.

[0018]FIG. 5A is a cross-sectional SEM photograph of a terminal bondingportion of an electrostatic chuck in comparative example 1.

[0019]FIG. 5B is an enlarged view of section B in FIG. 5A.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Various embodiments of the present invention will be describedwith reference to the accompanying drawings. It is to be noted that thesame or similar reference numerals are applied to the same or similarparts and elements throughout the drawings, and the description of thesame or similar parts and elements will be omitted or simplified.

[0021] A bonding member according to an embodiment of the presentinvention includes: a first member having a concave portion; a secondmember which is a member made of a different material from that of thefirst member and has a convex portion fitted to the concave portion; afirst bonding material which joins a bottom portion of the concaveportion of the first member and a tip portion of the convex portion ofthe second member and has a porous structure including particles andbrazing filler metal that covers a corner between tip and side portionsof the second member; and a second bonding material which includesbrazing filler metal that joins a side portion of the concave portion ofthe first member and a side portion of the convex portion of the secondmember.

[0022] As a combination of two or more of different kinds of members tobe used in the bonding member according to the embodiment of the presentinvention, enumerated are, for example: a combination of a ceramicsmember such as aluminum nitride and silicon nitride and a metal membersuch as molybdenum, Fe—Ni—Co alloy and tungsten; and a combination ofdifferent kinds of ceramics members which are made of different rawmaterials from each other. To be more specific, there is enumerated abonding member which is used in manufacture of a semiconductor wafer andis formed by connecting and joining an aluminum nitride member, whichexerts an electrostatic chuck function and a heater function by use ofbuilt-in metal electrodes and metal heating elements, and a metalmolybdenum member, for example, which is joined as a terminal supplyingpower to the built-in metal electrode member and the like.

[0023] Hereinafter, description will be given of the case, as anexample, where an electrostatic chuck is used as the bonding memberaccording to the embodiment of the present invention.

[0024]FIG. 1A shows an example of the electrostatic chuck according tothe embodiment of the present invention. The electrostatic chuckincludes: a substrate 2 including an electrode 3; and a terminal 1 whichsupplies power to the electrode 3. The substrate 2 has a rough discshape made of an aluminum nitride sintered body and has the electrode 3buried therein. The electrode 3 is made of metal such as molybdenum andmay be a wire mesh electrode or a screen printing electrode. At asupporting portion side of the substrate 2, the terminal 1 is buried. Anupper surface of the terminal 1 is connected to the electrode 3. An endface of the terminal 1 is exposed to a back of the substrate 2. Theterminal 1 is made of, for example, molybdenum subjected to goldplating.

[0025]FIG. 1B is an enlarged view of a bonding section of the terminal 1and the electrode 3, which are shown in FIG. 1A. FIG. 1B is turnedupside down from FIG. 1A. The substrate 2 has a concave terminal bondinghole 8 for joining the terminal 1. At a bottom of the concave terminalbonding hole 8, the electrode 3 is exposed. A tip portion of theterminal 1 and the electrode 3 are joined by a bottom portion bondingmaterial 4, and a side of the terminal 1 and a side of the terminalbonding hole 8 are joined by a side portion bonding material 5. In theterminal 1, a vertical direction vent hole 6 and a horizontal directionvent hole 7 are provided.

[0026] As shown in FIG. 1C, the bottom portion bonding material 4 joinsthe terminal 1 and the electrode 3 so as to cover a corner between thetip and side portions of the terminal 1. Moreover, a corner radius R1between the tip and side portions of the terminal 1 and a corner radiusR2 between the bottom and side portions of the terminal bonding hole 8are designed to have a relationship of R1≧R2×0.6. As described above,the corners of the terminal 1 and the terminal bonding hole 8 aredesigned. Thus, it is possible to effectively prevent cracks in a cornerportion where stress is concentrated. Furthermore, the corner radius R1between the tip and side portions of the terminal 1 is 0.3 mm or more.In a conventional electrostatic chuck, the corner radius R1 of theterminal 1 is as small as about 0.1 mm. Thus, by increasing the radiusas described above, it is made easier for the bottom portion bondingmaterial 4 to cover the corner.

[0027] The bottom portion bonding material 4, which is porous, may bemade of only brazing filler metal. However, it is preferable that thebottom portion bonding material 4 includes brazing filler metal andparticles. In order to lower thermal stress, as the particles, at leasttwo or more kinds of particles are used, which are different from thebrazing filler metal in wettability. The brazing filler metal andparticles having good wettability with the brazing filler metal andparticles having bad wettability with the brazing filler metal are mixedtogether and the brazing filler metal is melted. Accordingly, thebrazing filler metal permeates through the foregoing particles and abonding layer is formed. The brazing filler metal and the particles aremixed at a ratio of 70:30 to 10:90 and used. Moreover, the bonding maybe also made by previously filling a predetermined amount of particlesin bonding spots and pouring a predetermined amount of brazing fillermetal in its melted state thereinto. It is desirable that a thickness ofthe bottom portion bonding material 4 is 0.1 to 0.6 mm.

[0028] As the brazing filler metal used for the bottom portion bondingmaterial 4, enumerated are: one including noble metal, such as Au, Ag,Cu and Pd, as a base; a general-purpose brazing filler metal includingmetal, such as Al and Ni, as a base; and the like. There is noparticular limitation on the materials. Accordingly, more suitable onesmay be selected based on a relationship between the brazing filler metaland a property of a member to be joined. It is desirable that porosityof the bottom portion bonding material 4 after bonding is 20 to 80%.

[0029] Moreover, as the particles, suitably used are: ceramic particles;cermet particles which are a composite material of ceramic and metal;low thermal expansion metal particles; and the like. As the ceramicparticles, particles of silicon nitride, aluminum nitride, alumina,silicon carbide and the like are enumerated. As the cermet particles,particles of Ni—Al₂O₃, Cu—Al₂O₃ and the like are enumerated. As the lowthermal expansion metal particles, particles of metal such as molybdenumand tungsten, which have a low coefficient of thermal expansion at hightemperature, are enumerated. In order to efficiently lower the thermalstress, it is required to keep an average particle size of the materialsdescribed above within a fixed range. The average particle size ispreferably 1 to 100 μm, more preferably 30 to 80 μm. It is needless tosay that there is no harm in mixing two or more kinds of particleshaving different average particle sizes from each other and using themixture. In the case of using the ceramic particles, wettability thereofwith the brazing filler metal becomes a problem. Thus, it is required toplate a surface of the particles with metal such as Ni, Cu and Ag, forexample, or to cover the surface with coating of Au, Ag, Ti or the likeby sputtering. A plating method is not particularly limited. Electrolessplating and the like are suitably used. In this event, it is desirablethat a thickness of the plating is 1 to 5 μm.

[0030] Moreover, the wettability with the brazing filler metal differsby mixing coated particles and uncoated particles. Thus, porosity of thefirst bonding material after being joined can be controlled. A mixtureratio of the coated particles and the uncoated particles is preferablywithin 10:90 to 90:10, more preferably 30:70 to 70:30.

[0031] The side portion bonding material 5 includes brazing fillermetal. As the brazing filler metal used for the side portion bondingmaterial 5, enumerated are: one including noble metal, such as Au, Ag,Cu and Pd, as a base; a general-purpose brazing filler metal includingmetal, such as Al and Ni, as a base; and the like. There is noparticular limitation on the materials. Accordingly, more suitable onesmay be selected based on a relationship between the brazing filler metaland a property of a member to be joined. It is desirable that porosityof the brazing filler metal is 20 to 80%. The side portion bondingmaterial 5 has a two-layer structure. In the case of using brazingfiller metal of Al—Ni—Au, there are an Al-rich layer and an Al—Ni—Auintermetallic compound layer.

[0032] Moreover, it is desirable that a thickness of the side portionbonding material 5 is 0.008 to 0.012 times a diameter of the terminal 1.When the thickness thereof is 0.012 times the diameter or more, residualstress is increased by thermal expansion. Meanwhile, when the thicknessthereof is 0.008 times the diameter or less, there is only a hardintermetallic compound layer. Thus, a stress absorption effect is lost.In either case, cracks are likely to occur.

[0033] Moreover, the terminal 1 has therein a bonding material housinghole 9 which houses a bonding material for joining the terminal 1 andthe substrate 2 or the electrode 3. The terminal 1 having the bondingmaterial housed in the bonding material housing hole 9 is placed in theterminal bonding hole 8 and bonding is made. Thus, the terminal 1 can bejoined with the substrate 2 or the electrode 3.

[0034] Moreover, the terminal 1 has a vent hole running in a vertical orhorizontal direction in the terminal 1. The vent hole 6 or 7 can let gasescape to the outside, the gas being generated from the bondingmaterials in bonding. Thus, the bottom portion bonding material 4 andthe side portion bonding material 5 sufficiently permeate between theterminal 1 and the terminal bonding hole 8. Moreover, it is possible toprevent wicking of the bonding materials. FIG. 1B shows both of thevertical direction vent hole 6 and the horizontal direction vent hole 7.However, it is needless to say that the terminal 1 may have any one ofthe vent holes.

[0035] In the electrostatic chuck according to the embodiment of thepresent invention, the bottom portion bonding material 4 covers thecorner between the tip and side portions of the terminal 1. Thus, it ispossible to prevent cracks caused in the corner portion by theconcentrated stress. Accordingly, in the electrostatic chuck accordingto the embodiment of the present invention, cracks are unlikely to occurin the substrate, which includes a member vulnerable to thermal stress,in a cooling operation after bonding. Moreover, when the corner radiusbetween the tip and side portions of the terminal 1 is R1 and the cornerradius between the bottom and side portions of the terminal bonding holeis R2, the condition of R1≧R2×0.6 is satisfied. Accordingly, there is adifference between the corner radius of the terminal 1 and the cornerradius of the terminal bonding hole 8. Thus, it becomes easy for thebottom portion bonding material 4 to cover the corner of the tip portionof the terminal 1. Consequently, more sufficient covering is madepossible. Furthermore, the corner radius between the tip and sideportions of the terminal 1 is set as large as 0.3 mm or more. Thus, thebottom portion bonding material 4 can cover the corner of the tipportion of the terminal 1. Consequently, bonding strength between thesubstrate and the terminal can be maintained.

[0036] Similarly, in the bonding member according to the embodiment ofthe present invention, the first bonding material which joins the bottomportion of the concave portion of the first member (for example,ceramics member) and the tip portion of the convex portion of the secondmember (for example, metal member) and covers the corner between the tipand side portions of the second member. Thus, it is possible to preventcracks caused in the corner portion by the concentrated stress.Accordingly, in the bonding member according to the embodiment of thepresent invention, cracks are unlikely to occur in the substrate, whichincludes a member vulnerable to thermal stress, in a cooling operationafter bonding. Moreover, when the corner radius between the tip and sideportions of the convex portion 1 is R1 and the corner radius between thebottom and side portions of the concave portion is R2, the condition ofR1≧R2×0.6 is satisfied. Accordingly, there is a difference between thecorner radius of the convex portion and the corner radius of the concaveportion. Thus, it becomes easy for the first bonding member to cover thecorner of the convex portion. Consequently, more sufficient covering ismade possible. Furthermore, the corner radius between the tip and sideportions of the convex portion is set as large as 0.3 mm or more. Thus,the first bonding member can cover the corner of the convex portion.Consequently, bonding strength between different kinds of members can bemaintained.

[0037] Moreover, the bonding member according to the embodiment of thepresent invention has the vent hole penetrating in the vertical orhorizontal direction inside the convex portion from the bottom portionof the convex portion. This vent hole can let gas escape to the outside,the gas being generated from brazing materials or the like in bonding.Thus, the first and second bonding materials sufficiently permeatebetween the convex portion and the concave portion. Moreover, it ispossible to prevent wicking of the brazing filler metal.

[0038] Next, description will be given of a method for manufacturing theelectrostatic chuck according to the embodiment of the presentinvention. Here, with reference to FIG. 2, description will be given ofprocessing up to a stage before the terminal is joined.

[0039] (a) First, a material of the substrate is adjusted (S201).Specifically, as a raw material of the substrate of the electrostaticchuck, oxide additives are added to an aluminum nitride powder. As theoxide additives, yttria, ceria and the like are used. Thereafter, thealuminum nitride powder and the oxide additives are mixed. As a mixingmethod, for example, a large ball mill device called a trommel, in whicha container itself rotates, is used technically. Time required formixing by use of the trammel is, for example, about 30 minutes.Granulation is performed by adding a binder to the raw material powder.

[0040] (b) Next, powder calcination is performed (S202). Normally,calcination is performed after formation processing. However, in thecase of manufacturing an electrostatic chuck which has a buriedelectrode made of metal such as molybdenum, the electrode undergoesoxidation due to the calcination. Accordingly, the calcinations isperformed before the formation processing.

[0041] (c) Next, the electrode is buried and the formation processing ofthe aluminum nitride powder is performed (S203). As a forming method,cold isotropic pressing (Cold Isostatic Pressing: CIP) processing may beused, in which a uniaxial compact obtained by a mold forming method issubjected to isotropic forming processing to improve a compact densityand eliminate unevenness. It is also possible to obtain a compact byfilling a raw material powder directly in a rubber mold and performingthe CIP processing, without performing mold formation.

[0042] (d) Next, the aluminum nitride powder after formation is sinteredto produce an aluminum nitride sintered body (S204). As this sinteringmethod, an atmospheric pressure sintering method or hot pressing can beused. In the hot pressing, a raw material powder or a compact is filledin or inserted into carbon jigs and burned under uniaxial pressure of 30to 50 MPa. Accordingly, the hot pressing is suitable for burning of aceramics material which is hard to be densified by normal atmosphericpressure sintering. Furthermore, a hot isostatic pressing (HIP) method,in which the principle of CIP is applied to burning, can be also used.

[0043] (e) Next, the aluminum nitride sintered body is subjected toprocessing for placing the terminal (S205). Specifically, in thealuminum nitride sintered body to be the substrate, a concave terminalbonding hole for joining the terminal is formed. As this processing,cutting and polishing by use of diamond tools and the like areenumerated. Besides the above, ceramics processing by laser processing,ultrasonic machining, sand blasting or the like is also possible.

[0044] Next, with reference to FIG. 3, description will be given of astep of joining the terminal with the substrate of the electrostaticchuck.

[0045] (a) First, the terminal bonding hole of the substrate is cleaned(S301). The cleaning is performed by use of acetone, isopropyl alcohol(IPA), ammonia, pure water and the like. Thereafter, the bottom and sideof the terminal bonding hole is coated with about 1 to 5 μm of Niplating (S302). Next, a mixture of Ni-plated ceramic particles andunplated ceramic particles is laid on the Ni-plated bottom of the holeand is made smoothed.

[0046] (b) Meanwhile, as to the terminal, molybdenum is processed tohave a shape of the terminal and a nickel coating is applied thereto asan undercoat. Thereafter, the terminal is coated with about 10 μm ofgold plating. Before the plating, the corner radius R1 between the tipand side portions of the terminal is set to 0.3 mm or more. Moreover,the corner radius R1 between the tip and side portions of the terminaland the corner radius R2 between the bottom and side portions of theterminal bonding hole are processed to have a relationship of R1≧R2×0.6.Moreover, the bonding material housing hole 9 is formed in the tip ofthe terminal and the vent holes 6 and 7, which are connected to thebonding material housing hole 9, are formed in the terminal. Thereafter,particles are filled in the bottom portion so as to cover the cornerbetween the bottom and side portions of the terminal bonding hole 8.Subsequently, the terminal 1 having brazing filler metal set in thebonding material housing hole 9 is placed in the terminal bonding hole 8(S303).

[0047] (c) Next, a load is applied to the substrate 2 from above theterminal 1 (S304). The load is, for example, about 125 g. Subsequently,bonding is performed in a vacuum furnace (S305). As conditions of thebonding, for example, the substrate is heated at 700° C. for 10 minutes.In this event, the brazing filler metal set in the bonding materialhousing hole 9 of the terminal 1 is melted to permeate through theparticles. Thus, a bonded composition including the brazing filler metaland the particles forms the bottom portion bonding material 4. Moreover,the brazing filler metal permeating through the side forms the sideportion bonding material 5. Thereafter, cooling processing is performed.Cooling time may be determined in consideration for characteristics ofdifferent kinds of members to be joined and the like. Normally, thecooling time is within 1 to 10 hours. It is more preferable to adopt anannealing method in the cooling operation since an influence of thermalstress can be significantly lowered. Note that the annealing methodmeans cooling performed for about twice the time spent for the normalcooling method or more. Thus, the annealing can minimize the influenceof the thermal stress on the bonding portion.

[0048] (d) Thereafter, the substrate is taken out of the vacuum furnaceand visual inspection, dimension measurement, strength test and the likeof the substrate are performed (S306).

[0049] By use of the method for joining different kinds of membersaccording to the embodiment of the present invention, the bottom portionbonding material 4 covers the corner between the tip and side portionsof the terminal 1 and thus occurrence of cracks in the corner portiondue to concentrated stress can be prevented. Thus, by use of the methodfor joining different kinds of members according to the embodiment ofthe present invention, cracks are likely to occur in the substrate,which includes a member vulnerable to thermal stress, in the coolingoperation during bonding. Moreover, when the corner radius between thetip and side portions of the terminal 1 is R1 and the corner radiusbetween the bottom and side portions of the terminal bonding hole 8 isR2, the condition of R1≧R2×0.6 is satisfied. Accordingly, there is adifference between the corner radius of the terminal 1 and the cornerradius of the terminal bonding hole 8. Thus, it becomes easy for thebottom portion bonding material 4 to cover the corner of the tip portionof the terminal 1. Consequently, more sufficient covering is madepossible. Furthermore, the corner radius between the tip and sideportions of the terminal 1 is set as large as 0.3 mm or more. Thus, thebottom portion bonding material 4 can cover the corner of the tipportion of the terminal 1. Consequently, bonding strength between thesubstrate and the terminal can be maintained.

Other Embodiments

[0050] The present invention has been described according to theembodiment described above. It should be understood that the presentinvention is not limited to the description and drawings whichconstitute a part of the present disclosure. Various alternativeembodiments, embodiments and operational technologies will becomeapparent to those skilled in the art from the present disclosure.

[0051] For example, in the embodiment according to the presentinvention, the electrostatic chuck was described as an example of theconbonding member. Besides the electrostatic chuck, the presentinvention is also applicable to one in which two or more different kindsof members are joined by use of brazing filler metal and the like, forexample, a bonding member obtained by joining a porous ceramic memberand a metal member having a remarkably high coefficient of thermalexpansion and a bonding member obtained by joining ceramic membershaving different coefficients of thermal expansion from each other orjoining metal members having different coefficients of thermal expansionfrom each other. To be more specific, enumerated are: a bonding memberfor gas separation, which is formed by joining a porous alumina memberused for gas separation and a metal port member to be mounted on variousgas analyzers; and the like. It is needless to say that the bondingmember according to the present invention also includes a bonding memberformed by joining three or more different kinds of members.

[0052] Various modifications will become possible for those skilled inthe art after receiving the teachings of the present disclosure withoutdeparting from the scope thereof.

EXAMPLES

[0053] Examples and comparative examples of the present invention willbe described below. In the following examples and comparative examples,used was an electrostatic chuck that was a bonding member between asubstrate, which included a built-in electrode and was made of aluminumnitride, and a terminal which supplied power to the built-in electrodeand was made of gold-plated molybdenum. The electrode was a wire mesh.

Example 1

[0054] The electrostatic chuck was manufactured by the procedure shownin FIG. 2 and bonding of the substrate and the terminal was performed bythe procedure shown in FIG. 3. A diameter of the terminal used for thebonding was 5 mm. A corner radius R1 between tip and side portions ofthe terminal was set to 0.3 mm. Moreover, a corner radius R2 betweenbottom and side portions of a terminal bonding hole was set to 0.3 mm.In this event, as brazing filler metal, Al—Mg alloy was used. Asparticles, used were alumina particles having an average particle sizeof 40 μm, which were Ni-plated in a thickness of 1 to 2 μm. The brazingfiller metal and the particles were adjusted in a 1:1 ratio to obtain abottom portion bonding material 4. Moreover, Al—Ni—Au alloy was used asa side portion bonding material 5. A thickness of the bottom portionbonding material 4 was 0.3 mm and a thickness of the side portionbonding material 5 was 0.05 mm. A corner portion between the tip andside portions of the terminal 1 was covered with the bottom portionbonding material 4. Moreover, conditions of bonding were as below.

[0055] Bonding temperature: 700° C.

[0056] Retention time: 10 minutes

[0057] Atmosphere: vacuum (10-3 Pa)

[0058] The foregoing bonding test was performed for twenty electrostaticchucks and the number of electrostatic chucks which showed occurrence ofcracks was checked. The result is shown in Table 1. TABLE 1 Thickness ofTerminal Corner Corner side portion Number of no diameter radius R1radius R2 bonding occurrence of Yield No. (mm) (mm) (mm) material (mm)cracks (/20) (%) Example 1 5 0.3 0.3 0.05 19 95 Example 2 10 0.3 0.50.10 18 90 Comparative 5 0.3 0.8 0.05 10 50 Example 1 Comparative 10 0.30.8 0.10 9 45 Example 2 Comparative 5 0.5 0.3 0.02 10 50 Example 3Comparative 5 0.3 0.8 0.08 8 40 Example 4 Comparative 5 0.1 0.5 0.05 840 Example 5

[0059] It was confirmed that 19 out of the 20 electrostatic chucksshowed no occurrence of cracks and yields were 95%.

[0060] Moreover, FIGS. 4A and 4B show cross-sectional SEM photographs,each of which shows the terminal bonding portion used in the example 1.FIG. 4B is an enlarged view of the section A in FIG. 4A. The bottomportion bonding material 4 covers the corner portion of the terminal 1.Moreover, there is no occurrence of cracks in the corner portion.

Example 2

[0061] In the example 2, bonding was performed by using a terminal whichhad a diameter of 10 mm and a corner radius R1 of 0.3 mm between its tipand side portions. A corner radius R2 between bottom and side portionsof a terminal bonding hole 8 was set to 0.5 mm. A thickness of a sideportion bonding material 5 was 0.10 mm. The procedure for manufacturingan electrostatic chuck, the procedure for joining the terminal, kinds ofa bottom portion bonding material and the side portion bonding material,a thickness of the bottom portion bonding material and bondingconditions were similar to those of the example 1. Moreover, a cornerportion of the tip portion of the terminal was covered with the bottomportion bonding material 4. The foregoing bonding test was performed fortwenty electrostatic chucks and the number of electrostatic chucks whichshowed occurrence of cracks was checked. The result is shown in Table 1.

[0062] It was confirmed that 18 out of the 20 electrostatic chucksshowed no occurrence of cracks and yields were 90%.

Comparative Example 1

[0063] In the comparative example 1 for comparison with the examples 1and 2, bonding was performed by using a terminal which had a diameter of5 mm and a corner radius R1 of 0.3 mm between its tip and side portions.A corner radius R2 between bottom and side portions of a terminalbonding hole 8 was 0.8 mm. The procedure for manufacturing anelectrostatic chuck, the procedure for joining the terminal, kinds andthicknesses of a bottom portion bonding material and the side portionbonding material and bonding conditions were similar to those of theexample 1. Moreover, a corner portion of the tip portion of the terminalwas not covered with the bottom portion bonding material. The foregoingbonding test was performed for twenty electrostatic chucks and thenumber of electrostatic chucks which showed occurrence of cracks waschecked. The result is shown in Table 1.

[0064] It was confirmed that 10 out of the 20 electrostatic chucksshowed no occurrence of cracks and yields were 50%.

[0065] Moreover, FIGS. 5A and 5B show cross-sectional SEM photographs,each of which shows the terminal bonding portion used in the comparativeexample 1. FIG. 5B is an enlarged view of the section B in FIG. 5A. Thebottom portion bonding material 4 does not cover the corner portion ofthe terminal 1. In this event, there was occurrence of a crack C in thesubstrate 2 from the corner portion of the terminal 1.

Comparative Example 2

[0066] In the comparative example 2 for comparison with the examples 1and 2, bonding was performed by using a terminal which had a diameter of10 mm and a corner radius R1 of 0.3 mm between its tip and sideportions. A corner radius R2 between bottom and side portions of aterminal bonding hole 8 was 0.8 mm. The procedure for manufacturing anelectrostatic chuck, the procedure for joining the terminal, kinds andthicknesses of a bottom portion bonding material and the side portionbonding material and bonding conditions were similar to those of theexample 2. However, similar to the comparative example 1, a cornerportion of the tip portion of the terminal was not covered with thebottom portion bonding material 4. The foregoing bonding test wasperformed for twenty electrostatic chucks and the number ofelectrostatic chucks which showed occurrence of cracks was checked. Theresult is shown in Table 1.

[0067] It was confirmed that 9 out of the 20 electrostatic chucks showedno occurrence of cracks and yields were 45%.

Comparative Example 3

[0068] In the comparative example 3 for comparison with the examples 1and 2, bonding was performed by using a terminal which had a diameter of5 mm and a corner radius R1 of 0.5 mm between its tip and side portions.A corner radius R2 between bottom and side portions of a terminalbonding hole 8 was 0.3 mm. A thickness of a side portion bondingmaterial 5 was 0.02 mm. The procedure for manufacturing an electrostaticchuck, the procedure for joining the terminal, kinds of a bottom portionbonding material and the side portion bonding material, a thickness ofthe bottom portion bonding material and bonding conditions were similarto those of the example 1. However, similar to the comparative example1, a corner portion of the tip portion of the terminal was not coveredwith the bottom portion bonding material 4. The foregoing bonding testwas performed for twenty electrostatic chucks and the number ofelectrostatic chucks which showed occurrence of cracks was checked. Theresult is shown in Table 1.

[0069] It was confirmed that 10 out of the 20 electrostatic chucksshowed no occurrence of cracks and yields were 50%.

Comparative Example 4

[0070] In the comparative example 4 for comparison with the examples 1and 2, bonding was performed by using a terminal which has a diameter of5 mm and a corner radius R1 of 0.3 mm between its tip and side portions.A corner radius R2 between bottom and side portions of a terminalbonding hole 8 was 0.8 mm. A thickness of a side portion bondingmaterial 5 was 0.08 mm. The procedure for manufacturing an electrostaticchuck, the procedure for joining the terminal, kinds of a bottom portionbonding material and the side portion bonding material, a thickness ofthe bottom portion bonding material and bonding conditions were similarto those of the example 1. However, similar to the comparative example1, a corner portion of the tip portion of the terminal was not coveredwith the bottom portion bonding material 4. The foregoing bonding testwas performed for twenty electrostatic chucks and the number ofelectrostatic chucks which showed occurrence of cracks was checked. Theresult is shown in Table 1.

[0071] It was confirmed that 8 out of the 20 electrostatic chucks showedno occurrence of cracks and yields were 40%.

Comparative Example 5

[0072] In the comparative example 5 for comparison with the examples 1and 2, bonding was performed by using a terminal which had a diameter of5 mm and a corner radius R1 of 0.1 mm between its tip and side portions.A corner radius R2 between bottom and side portions of a terminalbonding hole 8 was 0.5 mm. A thickness of a side portion bondingmaterial 5 was 0.05 mm. The procedure for manufacturing an electrostaticchuck, the procedure for joining the terminal, kinds of a bottom portionbonding material and the side portion bonding material, a thickness ofthe bottom portion bonding material and bonding conditions were similarto those of the example 1. However, similar to the comparative example1, a corner portion of the tip portion of the terminal was not coveredwith the bottom portion bonding material 4. The foregoing bonding testwas performed for twenty electrostatic chucks and the number ofelectrostatic chucks which showed occurrence of cracks was checked. Theresult is shown in Table 1.

[0073] It was confirmed that 8 out of the 20 electrostatic chucks showedno occurrence of cracks and yields were 40%.

Conclusion

[0074] It was confirmed that the yields in the examples 1 and 2 were ashigh as 90 to 95% while the yields in the comparative examples 1 to 5were 40 to 50%. Therefore, it was confirmed that cracks were unlikely tooccur when the bottom portion bonding material 4 covered the cornerportion of the terminal. Furthermore, it was confirmed that cracks wereunlikely to occur when the corner radius R1 of the tip portion of theterminal was 0.3 mm or more. Moreover, in the examples 1 and 2, thecorner radius R1 between the tip and side portions of the terminal andthe corner radius R2 between the bottom and side portions of theterminal bonding hole satisfied the condition of R1≧R2×0.6. Furthermore,the thickness of the side portion bonding material 5 was 0.008 to 0.012times the diameter of the terminal in the examples 1 and 2 while thethickness thereof was outside of this value range in the comparativeexamples 3 and 4.

What is claimed is:
 1. A bonding member, comprising: a ceramics memberhaving a concave portion; a metal member which has a convex portionfitted to the concave portion; a first bonding material which joins abottom portion of the concave portion of the ceramics member and a tipportion of the convex portion of the metal member and has a porousstructure including particles and brazing filler metal that covers acorner between tip and side portions of the metal member; and a secondbonding material which includes brazing filler metal that joins a sideportion of the concave portion of the ceramics member and a side portionof the convex portion of the metal member.
 2. The bonding member ofclaim 1, wherein, when a corner radius between tip and side portions ofthe convex portion is R1 and a corner radius between bottom and sideportions of the concave portion is R2, a condition of R1≧R2×0.6 issatisfied.
 3. The bonding member of claim 1, wherein a corner radiusbetween tip and side portions of the convex portion is not less than 0.3mm.
 4. The bonding member of claim 1, further comprising a vent holewhich penetrates in any of a vertical direction and a horizontaldirection inside the convex portion from a bottom portion of the convexportion.
 5. An electrostatic chuck for absorbing an object to beprocessed, the electrostatic chuck, comprising: a substrate whichincludes an electrode therein and has a concave terminal bonding hole; aterminal which is a member made of a different material from that of thesubstrate and supplies power to the electrode; a bottom portion bondingmaterial which joins a bottom portion of the terminal bonding hole and atip portion of the terminal and has a porous structure includingparticles and brazing filler metal that covers a corner between tip andside portions of the terminal; and a side portion bonding material whichincludes brazing filler metal that joins a side portion of the terminalbonding hole and the side portion of the terminal.
 6. The electrostaticchuck of claim 5, wherein, when a corner radius between the tip and sideportions of the terminal is R1 and a corner radius between the bottomand side portions of the terminal bonding hole is R2, a condition ofR1≧R2×0.6 is satisfied.
 7. The electrostatic chuck of claim 5, wherein acorner radius between the tip and side portions of the terminal is notless than 0.3 mm.
 8. The electrostatic chuck of claim 5, wherein athickness of the side portion bonding material is 0.008 to 0.012 times adiameter of the terminal.
 9. The electrostatic chuck of claim 5, furthercomprising a bonding material housing hole which houses brazing fillermetal before bonding inside a convex tip of the terminal.
 10. Theelectrostatic chuck of claim 5, further comprising a vent hole whichpenetrates in any of a vertical direction and a horizontal directioninside the terminal from a bottom portion of the terminal.